A woman killed in a bus rollover northwest of Toronto on Wednesday has been identified as 56-year-old Radika Nankissoor.

Nankissoor died after a GO Transit bus crashed on Highway 407 in Vaughan, Ont., at approximately 10 p.m.

The bus was travelling east when it flipped over the guardrail and into the grass median near Weston Road. It had been driving from the Hamilton GO Centre to York University in the north end of Toronto.

Ontario Provincial Police Sgt. Kerry Schmidt told reporters on scene that six people were on the bus when it crashed.

Nankissoor was ejected when the bus crashed, and died at the scene. A representative of York University said that Nankissoor was a custodian at the school since 2010.

A witness who said he was first on scene told CTV Toronto that he helped get some of the passengers and the driver off the bus by kicking in the windows.

"When the officer showed up, we were walking around, we noticed that there was a lady underneath the wheel of the bus," he said.

Another bystander crawled into the bus to comfort one of the injured women who couldn't get out on her own.

"She was in a lot of pain, crying," the witness, Walter, said. She had blood on her face and was holding her side. She was rushed to hospital with the 66-year-old driver and another female passenger.

"Those people were bleeding from the head," he said.

A spokesperson for York University said one of the injured passengers was a current student, and the other was an alumnus.

The other two passengers escaped uninjured. The other passengers were all young adults between the ages of 18 to 23, Schmidt said.

"Our thoughts and prayers are with the families involved, the friends of the passenger who was killed in the accident as well as those who were injured and the bus driver," GO Transit President Greg Percy said at a news conference Thursday morning.

The bus driver has 15 years of experience, Percy told reporters. When asked if the driver had any pre-existing medical conditions, Percy said he couldn't comment further because of an ongoing police investigation.

The driver is still in hospital, recovering from his injuries.

Percy said the death was the first in GO Transit's history. Prior to Wednesday night, there had never been a death on a GO bus or train, he said.

The bus was significantly damaged during the crash, and the metal guardrail passed through the front of the bus and out the roof. Many of the windows were also broken.

The cause of the crash is still under investigation as police speak to witnesses and look for video surveillance footage.

The bus is an older model, so it did not have the video camera system present in some of the newer GO buses. It was equipped with a diagnostic computer, which will be reviewed by police and GO Transit.

There were no known mechanical issues on the bus at the time.

With files from CTV Toronto's Austin Delaney

Fatal GO Transit bus crash

A guardrail is seen inside a flipped GO Transit bus near Vaughan, Ont. on Thursday, Jan. 15, 2015. (Kerry Schmidt / OPP)

Go bus Crash Vaughan

Emergency personnel attend the scene of a rollover crash in Vaughan, Ont. on Wednesday, Jan. 14, 2015. (Victor Biro / THE CANADIAN PRESS)